The present invention relates generally to treating plaque deposits and occlusions within major blood vessels, more particularly to an apparatus and method for preventing detachment of mobile aortic plaque within the ascending aorta, the aortic arch, or the carotid arteries, and to an apparatus and method for providing a stent and a filter in a percutaneous catheter for treating occlusions within the carotid arteries.
Several procedures are now used to open stenosed or occluded blood vessels in a patient caused by the deposit of plaque or other material on the walls of the blood vessels. Angioplasty, for example, is a widely known procedure wherein an inflatable balloon is introduced into the occluded region. The balloon is inflated, dilating the occlusion, and thereby increasing intraluminal diameter. Plaque material may be inadvertently dislodged during angioplasty, and this material is then free to travel downstream, possibly lodging within another portion of the blood vessel or possibly reaching a vital organ, causing damage to the patient.
In another procedure, stenosis within arteries and other blood vessels is treated by permanently or temporarily introducing a stent into the stenosed region to open the lumen of the vessel. The stent typically comprises a substantially cylindrical tube or mesh sleeve made from such materials as stainless steel or nitinol. The design of the material permits the diameter of the stent to be radially expanded, while still providing sufficient rigidity such that the stent maintains its shape once it has been enlarged to a desired size.
Generally, a stent having a length longer than the target region is selected and is disposed on a catheter prior to use. The catheter typically has a flexible balloon, near its distal end, designed to inflate to a desired size when subjected to internal pressure. The stent is mounted to the catheter and compressed over the balloon, typically by hand, to assure that the stent does not move as it passes through the blood vessel to the desired location within the patient. Alternatively, self-expanding stents may also be used.
The stent is typically introduced into the desired blood vessel using known percutaneous methods. The catheter, having the stent securely crimped thereon, is directed to the region of the blood vessel being treated. The catheter is positioned such that the stent is centered across the stenosed region. The balloon is inflated, typically by introducing gas or fluid such as saline solution, through a lumen in the catheter communicating with the balloon. Balloon inflation causes the stent to expand radially, thereby engaging the stenosed material. As the stent expands, the material is forced outward, dilating the lumen of the blood vessel.
Due to substantial rigidity of the stent material, the stent retains its expanded shape, providing an open passage for blood flow. The balloon is then deflated and the catheter withdrawn.
Because the stent is often constructed from a mesh material, the stent typically compresses longitudinally as it expands radially. Stenotic material trapped between the stent and the vessel wall may extend into the openings in the mesh and may be sheared off by this longitudinal compression to create embolic debris free. When this material travels downstream, it can cause serious complications. For example loose embolic material released within the ascending aorta, the aortic arch, or the carotid arteries may travel downstream to the brain, possibly causing stroke, which can lead to permanent injuries or even death of the patient.
Thus, there is a need for an apparatus and method for delivering a stent into an arterial occlusion which substantially reduces the risk of embolic material escaping to the vessel and causing a blockage at a downstream location. There is also an apparatus and method for substantially preventing detachment of plaque deposited on the walls of the ascending aorta, the aortic arch, the descending aorta, and the carotid arteries. In addition, there is a need for an apparatus and method to substantially contain loose embolic material within the aorta and the carotid arteries during an interventional procedure, preventing it from reaching the brain.
The present invention provides an apparatus and method for preventing embolic material from escaping a site of intervention within the aorta, the carotid arteries, and other arteries generally, thereafter causing damage to vital organs, such as the brain. More particularly, the present invention involves an apparatus and method for introducing a stent into a region of a major blood vessel within the human body having plaque deposits, such as the ascending aorta, the descending aorta, aortic arch, common carotid artery, external and internal carotid arteries, brachiocephalic trunk, middle cerebral artery, anterior cerebral artery, posterior cerebral artery, vertebral artery, basilar artery, subclavian artery, brachial artery, axillary artery, iliac artery, renal artery, femoral artery, popliteal artery, celiac artery, superior mesenteric artery, inferior mesenteric artery, anterior tibial artery, and posterior tibial artery, thereby opening occlusions and/or preventing embolic material from breaking free within the blood vessel.
In a first embodiment, the invention includes a guidewire having an expandable filter attached to it, and a stent catheter. The catheter has an inflatable balloon mounted on or near its distal end, and an inflation lumen extending through the catheter between a proximal region of the catheter and the balloon. A stent is provided on the outer surface of the catheter, substantially engaging the balloon. Generally, the stent comprises an expandable substantially rigid tube, sheet, wire or spring, but preferably a cylindrical mesh sleeve. See Palmaz, U.S. Pat. No. 4,733,665, incorporated herein by reference.
Alternatively, the stent may be a self-expanding sleeve, preferably from nitinol. In this case, the stent catheter does not require an inflatable balloon. Instead the stent is compressed over the catheter and a sheath or outer catheter is directed over the stent to hold it in the compressed condition until time of deployment.
The guidewire has a filter assembly attached at or near its distal end, which includes an expansion frame which is adapted to open from a contracted condition to an enlarged condition. Filter material, typically a fine mesh, is attached to the expansion frame to filter undesirable embolic material from blood.
The guidewire with the expansion frame in its contracted condition is provided through a sheath or cannula, or preferably is included directly in the stent catheter. The catheter typically has a second lumen extending from its proximal region to its distal end into which the guidewire is introduced. The filter assembly on the distal end of the guidewire is then available to be extended beyond the distal end of the catheter for use during stent delivery.
The device is typically used to introduce a stent into a stenosed or occluded region of a patient, preferably within the carotid arteries. The catheter is introduced percutaneously into a blood vessel and is directed through the blood vessel to the desired region. If the filter device is provided in a separate sheath, the sheath is percutaneously inserted into the blood vessel downstream of the region being treated, and is fixed in position.
The filter assembly is introduced into the blood vessel, and the expansion frame is opened to its enlarged condition, extending the filter mesh substantially across the blood vessel until the filter mesh substantially engages the walls of the vessel.
The catheter is inserted through the region being treated until the stent is centered across the plaque deposited on the walls of the blood vessel. Fluid, preferably saline solution, is introduced through the inflation lumen, inflating the balloon, and expanding the stent radially outwardly to engage the plaque. The stent pushes the plaque away from the region, dilating the vessel. The balloon is deflated, and the catheter is withdrawn from the region and out of the patient. The stent remains substantially permanently in place, opening the vessel and trapping the plaque beneath the stent.
When the stenosed region is opened, embolic material may break loose from the wall of the vessel, but will encounter the filter mesh and be captured therein, rather than traveling on to lodge itself elsewhere in the body. After the stent is delivered, the expansion frame is closed, containing any material captured in the filter mesh. The filter assembly is withdrawn back into the sheath or the catheter itself, which is then removed from the body.
If a self-expanding stent is used, the stent catheter with the compressed stent thereon is inserted into a sheath, which restrains the stent in a compressed condition. The catheter is introduced into the patient""s blood vessel and directed to the target region. Once the stent is localized across the stenosed region and the filter assembly is in position, the sheath is drawn proximally in relation to the catheter. This exposes the stent, which expands to engage the wall of the blood vessel, opening the lumen. The filter assembly is then closed and the catheter withdrawn from the patient.
The filter assembly has a number of preferred forms. For example, the expansion frame may comprise a plurality of struts or arms attached to and extending distally from the distal end of the guidewire. The struts are connected to each other at each end and have an intermediate region which is biased to expand radially. Filter mesh is attached typically between the intermediate region and the distal ends of the struts, thereby defining a substantially hemispherical or conical shaped filter assembly.
To allow the filter assembly to be inserted into the lumen of the sheath, the intermediate region of the expansion frame is compressed. When the filter assembly is ready to be introduced into a blood vessel, the guidewire is pushed distally. The expansion frame exits the lumen, and the struts automatically open radially. This expands the filter mesh to substantially traverse the vessel. After the stent is delivered, the guidewire is pulled proximally to withdraw the filter assembly. The struts contact the wall of the filter lumen, forcing them to compress, closing the frame as the filter assembly is pulled into the sheath.
In another embodiment, the expansion frame includes a plurality of struts attached to the distal end of the sheath. The struts extend distally from the sheath and attach to the distal end of the guidewire which is exposed beyond the sheath. At an intermediate region, the struts are notched or otherwise biased to fold out radially. Filter mesh is attached to the struts between the intermediate region and the distal end of the guidewire.
The filter assembly is directed into position in the blood vessel, either exposed on the end of the sheath or preferably within a second sheath which is withdrawn partially to expose the filter assembly. With the sheath fixed, the guidewire is pulled proximally. This compresses the struts, causing them to bend or buckle at the intermediate region and move radially outwardly, expanding the filter mesh across the blood vessel. After use, the guidewire is pushed distally, pulling the struts back down and closing the filter mesh.
In an alternative to this embodiment, the struts attached to the distal end of the sheath and to the distal end of the guidewire are biased to expand radially at an intermediate region. The filter mesh is attached to the struts between the intermediate region and the distal end of the guidewire. Prior to introduction into a patient, the guidewire is rotated torsionally in relation to the sheath, twisting the struts axially around the guidewire and compressing the filter mesh. Once in position in the blood vessel, the guidewire is rotated in the opposite direction, unwinding the struts. The struts expand radially, opening the filter mesh. After use, the guidewire is rotated once again, twisting the struts and closing the filter mesh for removal.
In yet another embodiment, the filter assembly comprises a plurality of substantially cylindrical compressible sponge-like devices attached in series to the guidewire. The devices have an uncompressed diameter substantially the same as the open regions of the blood vessel. They are sufficiently porous to allow blood to pass freely through them but to entrap undesirable substantially larger particles, such as loose embolic material.
The devices are compressed into the lumen of the sheath prior to use. Once in position, they are introduced into the blood vessel by pushing the guidewire distally. The devices enter the vessel and expand to their uncompressed size, substantially engaging the walls of the blood vessel. After use, the guidewire is pulled proximally, forcing the devices against the distal end of the sheath and compressing them back into the lumen.
In a second embodiment, a stent catheter and filter assembly are also provided. Unlike the previous embodiments, the filter assembly is not primarily mechanically operated, but is instead, generally fluid operated. Typically, the stent catheter includes a second balloon on or near the distal end of the catheter. A second inflation lumen extends through the catheter from the proximal region of the catheter to the balloon. The balloon is part of the expansion frame or alternatively merely activates the expansion frame, opening the filter assembly to the enlarged condition for use and closing it after being used.
In one form, the balloon has an annular shape. Filter mesh is attached around the perimeter of the balloon, creating a conical or hemispherical-shaped filter assembly. A flexible lumen extends between the balloon and the inflation lumen within the catheter. Optionally, retaining wires are connected symmetrically between the balloon and the catheter, thereby holding the balloon substantially in a desired relationship to the catheter.
When deflated, the balloon substantially engages the periphery of the catheter, holding the filter mesh closed and allowing the catheter to be directed to the desired location. Once the catheter is in position, the balloon is inflated. The balloon expands radially until it engages the walls of the blood vessel, the filter mesh thereby substantially traversing the vessel. After use, the balloon is deflated until it once again engages the perimeter of the catheter, thereby trapping any embolic material between the filter mesh and the outer wall of the catheter.
Alternatively, the balloon of this embodiment may be provided on the catheter proximal of the stent for retrograde use. In this case, the filter mesh is extended between the balloon and the outer surface of the catheter, instead of having a closed end.
In a third embodiment of the present invention, a method is provided in which a stent catheter is used to prevent the detachment of mobile aortic deposits within the ascending aorta, the aortic arch or the carotid arteries, either with or without an expandable filter assembly. A stent catheter, as previously described, is provided having an inflatable balloon and a stent thereon, or alternatively a self-expanding stent and a retaining sheath. The catheter is percutaneously introduced into a blood vessel and is directed to a region having mobile aortic plaque deposits, preferably a portion of the ascending aorta or the aortic arch.
The stent is positioned across the desired region, and the balloon is inflated. This expands the stent to engage the plaque deposits and the walls of the blood vessel, thereby trapping the plaque deposits. The balloon is deflated, and the catheter is removed from the blood vessel. Alternatively if a self-expanding stent is used, the sheath is partially withdrawn proximally, and the stent is exposed, allowing it to expand. The stent substantially retains its expanded configuration, thereby containing the plaque beneath the stent and preventing the plaque from subsequently detaching from the region and traveling downstream.
Optionally, a filter device similar to those already described may be introduced at a location downstream of the treated region. The filter device may be provided in a sheath which is inserted percutaneously into the blood vessel. Preferably, however, a filter device is attached to the stent catheter at a location proximal to the stent. Instead of attaching the filter assembly to a guidewire, it is connected directly to the outer surface of the catheter proximal to the stent. A sheath or cannula is typically provided over the catheter to cover the filter assembly.
Once the catheter is in position within the vessel, the sheath is withdrawn proximally, the filter assembly is exposed and is expanded to its enlarged condition. In a preferred form, the expansion frame includes biased struts similar to the those described above, such that when the filter assembly is exposed, the struts automatically expand radially, and filter mesh attached to the struts is opened. After the stent is deployed, the sheath is moved proximally, covering the expansion frame and compressing the struts back into the contracted condition. The catheter and sheath are then withdrawn from the patient.
Thus, an object of the present invention is to provide an apparatus and method for substantially preventing mobile aortic plaque deposited within the ascending aorta, the aortic arch, or the carotid arteries from detaching and traveling to undesired regions of the body.
Another object is to provide an apparatus and method for treating stenosed or occluded regions within the carotid arteries.
An additional object is to provide an apparatus and method for introducing a stent to treat a stenosed or occluded region of the carotid arteries which substantially captures any embolic material released during the procedure.